Controlled release composition of biocide in an aqueous dispersion of viscous oil

ABSTRACT

A controlled release agricultural composition comprising an aqueous dispersion of: 1) a water insoluble matrix comprising a viscous oil (i.e., a hydrocarbon crude oil or post-refining residual oil) selected from the group consisting of bitumen, abietic acid, ester derivatives of abietic acid, carboxylic acid containing materials, and carboxylic acid ester containing materials, and 2) at least one active ingredient, which has a melting point of less than 140° C. and is soluble in the viscous oil matrix, selected from the group consisting of herbicides, insecticides, fungicides, and nematicides.

FIELD OF THE INVENTION

This invention relates to improved controlled release compositions thatallow an active ingredient to be released in a controlled manner, and inparticular to such compositions that are in the form of aqueousdispersions. The invention also relates to methods of preparingcontrolled release compositions in the form of an aqueous dispersion.

1. Background of the Invention

Controlled release formulations in the form of aqueous emulsions havebeen previously disclosed in PCT/AU 89/00230.

There are several ways in which the use of such types of controlledrelease formulations in the form of aqueous dispersions can be ofincreased benefit relative to known compositions of active.

1. The controlled release formulation may decrease the rate of releaseof active ingredient from the formulation, leading to a longer period ofefficacy or, if the active is volatile, leading to reduced loss ofactive to the atmosphere.

2. The controlled release formulation may be safer to handle and store.

3. The controlled release formulation may contain less volatile solvent.

4. The controlled release formulation may be less harmful to beneficialspecies. For example, a controlled release cereal herbicide may be lessdamaging to germinating wheat than a standard formulation such as anemulsion concentrate.

5. The controlled release formulation may enhance the potency of theactive ingredient, for example by improving the uniformity ofdistribution of the active ingredient in soil.

2. Summary of Prior Art

Previous aqueous dispersions for the controlled release of activeingredients have included the following types:

a. Dispersions where a chemical reaction occurs after the formation ofthe dispersion, creating a solid matrix from an originally liquiddisperse phase. Examples include the formulation of poly-urea capsulesand the formation of a polymer matrix from liquid monomers bypolymerisation. Specific examples are disclosed in Australian PatentApplication No. 37393/85 and U.S. Pat. No. 3,212,967.

b. Dispersions where an organic solvent is removed from the dispersephase after the formation of the dispersion, leaving a solid dispersemass as host matrix, for example the formation of polylactidemicro-capsules. An example is disclosed in Japanese Patent ApplicationNo. 48923/85.

c. Dispersions in which a solid coating is formed on the outer boundaryof the disperse phase by the process of polymer coacervation (i.e.controlled precipitation of polymers at the interface). An example isdisclosed in British Patent No. 929405.

d. Dispersions in which the matrix is heated to elevated temperaturesprior to the addition of the active ingredient or ingredients, and inwhich the molten mass is added with vigorous stirring to an aqueousphase in the presence of surfactants to form a stable emulsion.

This last type of dispersion has been alleged to be useful in thefollowing cases:

(i) Composition for the protection of wood using a dispersion offungicide and insecticide in an oily matrix (Pojurowski French PatentPublication No. 2,392,787).

(ii) Composition with improved biocidal properties using a dispersione.g. of pentachlorophenol in paraffin (Mobil Australian PatentApplication No. 19222/70). In this instance, it was observed that thedispersions were also useful for imparting water resistant properties totreated surfaces (e.g. wood).

Using these compositions, the delivery of active ingredient at the siteof application of the composition may occur at a reduced rate whencompared with the performance of standard compositions of the sameactive substance.

In many cases it is important to decrease the rate of release of activeingredient from the controlled release formulation relative to the rateof release of active from the standard formulation by a considerableamount before significant product advantages can be obtained. Thisadvantage is usually sought in terms of increased efficacy of thecontrolled release formulation. See for example, the publication ofMarvin M. Schreiber et al in "Weed Science" Vol 35 No. 3 pages 407-11(1987).

The required reduction of release rate in the controlled release productdepends on both the nature of the active ingredient and on theperformance of the standard formulation of the active material.

It is an object of the present invention to provide improved controlledrelease compositions and in particular controlled release formulationsof dinitroaniline herbicides, chloroacetanilide herbicides andorganophosphate insecticides, preferably trifluralin, metolachlor andchlorpyrifos where the formulations show decreased volatile loss ofactive ingredient and/or reduced phytotoxicity to crops in fieldapplicants and/or increased or equal efficacy.

The invention also relates to methods of preparing controlled releasecompositions in the form of aqueous dispersions.

The term "viscous oil" is defined for the purposes of this invention asany naturally occurring hydrocarbon crude oil or any residual oilremaining after refining operations which is generally characterised bya viscosity of about 10² -10⁶ centipoise or greater and otherwisegenerally, but not necessarily, characterised by an API gravity of about20° API or less, high metal content, high sulfur content, highasphaltene content and/or high pour point. The term "viscous oil" it isto be understood also to encompass the following: vacuum residuals,vis-breaker residuals, catalytic-cracker residuals, catalytichydrogenated residuals, coker residuals, ROSE (residual oilsupercritical extraction) residuals, tars and cut-back tars, bitumen,pitch and any other terms describing residuals of hydrocarbonprocessing. The term "viscous oil" encompasses naturally occurringviscous crude oils (also called heavy crude oils) as well as residualbottom-of-the-barrel products from refineries, such as vacuum residuesand other residual fuel oils and asphalt. While low gravity does notnecessarily coincide with high density, these characteristics aregenerally correlated in viscous hydrocarbons.

Generally the following characteristics are considered typical of thetypes of crude oils and residual oils which are useful for the presentinvention.

1. Low API gravity, generally at or below 20° API. This is the mostfrequently use criterion, both because it is easily measured and because20° API crude roughly corresponds to the lower limit recoverable withconventional production techniques.

2. Viscosities in the range of about 10² to 10⁶ centipoise (cp) or evenhigher in some cases. For those materials that are solids at ambienttemperatures it is a requirement that they have a viscosity of at least100 centipoise at 120° C.

3. High metal contents. For example, heavy crudes often have nickel andvanadium contents as high as 500 ppm.

4. High sulfur content, eg, 3 weight percent or more.

5. High asphaltene content.

6. High pour point.

The "viscous oils" can be generally defined as having a paraffin contentof about 50% by weight or less and an aromatic content of about 15% byweight or greater with viscosities of about 100 centipoise or greater at65°. The viscous residuals generally are characterised by a paraffincontent in the range from about 4% to about 40% by weight, an aromaticcontent in the range from about 15% to about 70% by weight and anasphaltene content from about 5% to about 80% by weight.

In addition, the term "viscous oil" includes heads and bottoms of crudetall oil (a wood derivative) abietic acid, especially as wood rosin andchemical derivatives of abietic acid eg, the maleic anhydride adduct ofabietic acid and especially chemical derivatives of abietic acid whichexhibit ester functionality, eg the condensation product of abieticacid, maleic anhydride and glycerol. Other polyhydric alcohols may alsobe used, though glycerol is preferred. Other viscous hydrocarbonssuitable for this invention are the bottoms of any distillation columnof processes used to extract natural oils eg, eucalyptus oil.

In addition, the term "viscous oil" includes substances which are solidat room temperature but become viscous oils as described herein in therange 20°-120° C.

Preferably the "viscous oil" is selected from heads and bottoms of crudetall oil, distillation bottoms of oil extraction processes (oil ofmineral natural vegetable or animal origin), wood rosin, and derivativesof wood rosin. More preferably the "viscous oil" is selected frombitumen, wood rosin, derivatives of wood rosin with ester functionalityand mixtures of above. The "viscous oil" may also be selected frommaterials having carboxylic acid groups or carboxylic acid ester groupssuch as maleic ester residues.

Stabilising amounts of surfactants are present in compositions of ourinvention. Combinations of surfactant types such as non-ionic andanionic are particularly useful. Preferred ionic surfactants are:calcium dodecyl benzene sulphonate (linear or branched chain), metal andamine salts of organic acids (eg, stearic, oleic and abietic acid) amineethoxylates and primary, secondary and tertiary alkylamines.

Preferred non-ionic surfactants are amine ethoxylates and alkylphenolethoxylates and ethoxylates and propoxylates of polyhydric alcohols suchas sorbitol and glycerol. Other preferred suffactants are copolymers ofpolyoxyethylene and polyoxypropylene, and alkyl and alkylphenol adductsof such copolymers.

Further preferred surfactants are Vinsol (trademark of Hercules PryLtd), alpha oleum sulphonate, alkyl dimethyl benzyl ammonium chlorideand cetyl trimethyl ammonium bromide.

Preferably a mixture of ionic and non-ionic surfactants are used andespecially preferred are combinations of anionic and non-ionicsurfactants.

Any of the surfactants of the formulation may be added to the oil phaseor the aqueous phase, or to both.

In choosing the appropriate surfactants for the invention, the physicalstability of the emulsion was an important criteria. Stability ensuresthat there is adequate shelf stability for a commercial product.

Stability of emulsions was assessed using the following criteria:

i) Particle Size

Emulsions were diluted, 1% in water and viewed under a microscope. Asubjective determination of common particle size range was performed anddegree of flocculation was also noted.

ii) Dispersability in Water

Emulsions were diluted 1% in water and ease of dispersion was assessedby eye.

iii) Appearance and Colour

The colour and appearance of the emulsion was observed immediately afterpreparation. The colour was used as an initial estimation of particlesize. For coloured matrices, a paler appearance was taken to indicatesmaller particle size.

iv) Bench Stability

Inversion: The resistance of emulsions was measured to ensure emulsionswere water external. This was performed with a multimeter using standardprocedure.

Phasing: Any gross settling of particles was deemed unacceptable asdetermined by the eye.

Crystallisation: The surface and bulk of emulsions were inspectedregularly by eye to note the first signs of crystallization and hencefailure to yield a stable emulsion. Results were confirmed byexamination of emulsions under an optical microscope using crossedpolarising lenses.

The following studies used trifluralin as the active material andbitumen as the matrix material. A range of nonionic surfactantsincluding: nonyl phenol ethoxylates, other fatty alcohol ethoxylates,and fatty amine ethoxylates was evaluated in combination with an anionicemulsifier. The ratio of anionic emulsifier (e.g. vinsol resin) andnonionic emulsifier and the HLB of the various nonionic surfactants wereinvestigated over a number of differing ratios. Emulsions were preparedusing these surfactant systems and were assessed according to thecriteria listed above (see Table I). All of the emulsions based on thevinsol resins displayed totally unacceptable stability, (that is theemulsions inverted, produced massive crystallization or gross synerysison storage at ambient temperatures over periods of time from 1 hour to 2weeks.

Due to the unacceptable performance of the vinsol resin anionicsurfactants different types of anionic emulsifiers were investigated.Fatty acids neutralised with amine or metal salts in combination withfatty amine ethoxylates were found to yield emulsions with improvedstability. Different fatty acids, including oleic acid, linoleic acid,lauric acid, stearic were assessed in combination with fatty amineethoxylates of various HLB values. Emulsions were prepared usingcombinations of fatty acids and amine ethoxylates and the surfactantswere optimised to yield the best emulsion stability.

Concomitantly fatty quaternary ammonium surfactants in combination withfatty alcohol ethoxylates were also found to yield emulsions withimproved stability. However, the viscosity of these emulsions was toohigh and led to poor dispersability in water.

Another class of surfactants investigated was calcium dodecyl benzenesulphonate in combination with alkyl and alkylaryl polyoxyalkylene oxideether condensates. These suffactants were found to yield emulsions withparticle sizes typically less than 2 um treat displayed excellentdisperability and suspendability when diluted in water and good shelfstability. Again, the ratio of anionic to nonionic emulsifier wasadjusted to optimise emulsion stability. (see Table I).

The resulting emulsion using bitumen as the controlled release matrixhad a viscosity of 1500 cp. The droplet size of the emulsion wastypically less than 2 um. After two months storage at ambienttemperature there was no sign of trifluralin crystallization, dropletcoalescene or emulsion deterioration as determined by techniques wellknown in the art.

For bitumen matrix at high oil ratios we departed from the conventionalan by dissolving all nonionic and ionic emulsifier components in theaqueous phase. This preferred method was found to yield emulsions ofsuperior stability with smaller particle size, less prone tocrystallization. It is thought that dissolving the suffactants in theaqueous phase enables rapid migration of suffactants to the interfaceand hence minimization of particle size.

The conventional art as applied to bitumen containing emulsionsdiscloses the use of certain anionic suffactants (eg vinsol mixed witholeic and neutralised to pH 12) or blends of anionic and nonionicsurfactants (eg ameroxyl OE10 (high HLB), plus vinsol neutralised to pH12 in the aqueous phase, and Ameroxyl OE2 (low HLB) in the non-aqueousphase. The purpose of neutralising vinsol to PHI2 was to promote theanionic character of the emulsifier. The role of the nonionic surfactantwas to achieve a degree of steric stabilisation. This was not achievedto an adequate extent because the conventional systems were shown to beunstable (Table 1).

                                      TABLE 1                                     __________________________________________________________________________    CHARACTERISTICS OF BITUMEN EMULSIONS                                          Surfactant System                                                             Nonionic   Ionic      % Phasing                                                                             Presence of                                                                           Common Particle  Dispersability         Type     % Type     % after 2 weeks                                                                         Crystalization                                                                        Size Range (um)                                                                         Colour in                     __________________________________________________________________________                                                           Water                  Fatty    80                                                                              Vinsol   20                                                                              20      --      Large drops                                                                             Dark Brown                                                                           Very Poor              C.sub.17 alcohol/                                                                        Resin                      >100                                    6 ethylene oxide                                                              Fatty    89                                                                              Vinsol   20                                                                              6       2 weeks crystals                                                                      1-40      Dark Brown                                                                           Poor                   C.sub.17 alcohol/                                                                        Resin              throughout                                      6 ethylene oxide                                                              Medium chain                                                                           40                                                                              Calcium  60                                                                              0       --      <1        Pale Brown                                                                           Excellent              alkyl phenol                                                                             Dodecyl                                                            propoxylate/                                                                             Benzene                                                            ethoxylate Sulphonate                                                         Medium chain                                                                           50                                                                              Calcium  50                                                                              0       --      <1        Pale Brown                                                                           Excellent              alkyl phenol                                                                             Dodecyl                                                            propoxylate/                                                                             Benzene                                                            ethoxylate Sulphonate                                                         C.sub.16 fatty                                                                         50                                                                              Tall Oil 50                                                                              0       --      2-20      Dark Brown                                                                           Good                   amine/     Fatty                                                              5 ethylene oxide                                                                         Acid + NaOH                                                        __________________________________________________________________________

The stability of surfactant systems was investigated by looking atclasses of surfactants which were anticipated to promote a sufficientdegree of steric stabilisation and charge stabilisation in the dispersedphase and promote fine droplet size. Surfactants were selected on thebasis of the following characteristics:

Ionic suffactants displaying low water solubility, molecular weight inthe range of from 100-400 a.m.u. It was thought that suffactantsdisplaying the above characteristics would provide a uniform chargedistribution over the dispersed particle droplets and promote goodinterfacial packing with elected non-ionic emulsifiers.

Non-ionic suffactants with relatively high molecular weight (1500-4000),high HLB (12-17), and potential multiple anchoring sites to promotestrong adhesion to the dispersed particle surface. For example alkylphenol propoxylates/ethoxylates are suitable.

Blends of anionic and non-ionic suffactants displaying the abovecharacteristics were mixed to optimum ratios. Optimum ratios weredetermined by screening the different blends of anionic and non-ionicsuffactants using criteria (i-iv) as described above. Ratios of between80:20 to 20:80 anionic:nonionic were found to work. For example usingbitumen/trifluralin preferably surfactant ratios of from 60:40 to 40:60were utilised (see Examples 4 and 5). The most preferredanionic:nonionic surfactant ratio was 50:50 (Example 6).

It is believed that the above ratios worked because the propylene oxideblock in the nonionic surfactant provides multiple anchoring sites onthe dispersed particles which promote strong adhesion characteristics tothe particles and allowed the ethylene oxide component of the nonionicsurfactant to effectively stabilise the droplets through stericstabilisation and helped reduce interfacial tension between the aqueousphase and non-aqueous phases. This is also thought to help to promotefine particle size.

It is thought that the choice of anionic surfactant provides for an evendistribution of low level charge sufficient to assist stabilisation ofthe emulsion particles but not high enough to affect viscosity of theemulsion. It is for the above reasons that the combination of the twoanionic and nonionic surfactants described above are thought to packtogether at the interface and by so doing stabilise the emulsiondroplets. Preferred anionic surfactants are calcium dodecyl benzenesulphonate, metal and amine salts of fatty acids (especially linoleicand oleic), resin acids and high molecular weight polyacrylic acidstabilisers.

Above-mentioned blends of anionic and nonionic surfactants, albeit atvarying ratios were found to be efficient for synthesis of the followingemulsions:

1. trifluralin in abietic acid together with volatile and non volatilesolvents.

2. chlorpyrifos in abietic acid and in resin based on the condensationof glycerol and abietic acid, together with volatile and non-volatilesolvents.

3. metolachlor in bitumen, together with volatile and non-volatilesolvents.

Typically the particle size of the disperse phase is less than 50microns diameter and more usually less than 10 microns and even moreusually less than 5 microns diameter. The formulations may also compriseone or more solvents for the active ingredient. Such solvents may bevolatile, eg xylene and Solvesso 100. Solvesso 150 or Solvesso 200 and1,1,1 tricholoroethane, or non-volatile such as paraffin or oleic acidor water-immiscible liquids with ester functionality. Solvesso 100, 150and 200 are proprietary high aromatic volatile hydrocarbon solventshaving different boiling point ranges. Solvesso is a trademark of ShellAustralia. Examples of non-volatile liquids are esters of phthalic acidand of other fatty acids e.g. oleic acid and of abietic acid, andoligomeric and polymeric condensates of di-acids such as condensates ofadipic acid and polyethylene glycol. The preferred esters are loweralkyl esters of oleic and abietic acid and the most preferred are methyloleate and ethyl oleate. The above-mentioned blends of surfactants (atvarious ratios) were also found useful for non-bitumen emulsions.

The relative proportions of the viscous oil, active ingredient,surfactants, and solvents if present, are important to the working ofthe invention. The insoluble phase, being the combination of viscous oiland active is 10-80% w/w of the composition, more preferably 30-75% andmost preferably 50-70%. It should be noted however that thesepercentages relate to compositions in the form that they aremanufactured and transported. Clearly the lower the concentration ofwater present in the composition the more cost efficient are transportand packaging costs. In the most preferred compositions the water levelis less than 30% by weight. However, compositions of the presentinvention may be diluted by the applicator of the formulation bytypically 30 parts of water to 1 part of controlled release formulation.

The active ingredient is selected from the range of agriculturalchemicals consisting of herbicides, fungicides, nematicides andinsecticides. Preferably the active ingredient has a melting point lessthan 140° C. more preferably less than 100° C. and most preferably <80°C.

Especially preferred herbicides are the dinitroaniline class,particularly trifluralin and the chloroacetanilide class, particularlymetolachlor. Preferred insecticides are the organophosphate class,particularly chlorpyrifos. In the compositions of the present inventionthe preferred levels of active are 3-70% w/w and most preferably 10-55%.

The volatile solvent e.g. Solvesso 150 is used up to 50% w/w morepreferably up to 35% w/w and most preferably up to 25% w/w of thecomposition.

The non-volatile solvent is preferably a water insoluble liquid havingester functionality, e.g. phthalate di-esters or polyesters comprisingadipic acid residues. More preferably the non-volatile solvent isselected from the group consisting lower alkyl esters of fatty acids orabietic acid, particularly methyl and ethyl esters.

Preferably the non-volatile solvent is used up to 40% w/w, morepreferably up to 20% and most preferably up to 12%.

The aqueous phase of the formulation may contain additives to controlthe rheology and cold temperature storage properties of the dispersion.Examples of such additives are polyhydric alcohols such as glycerol,ethylene glycol, propylene glycol, sorbitol, polyethylene glycol andpolypropylene glycol, Aqueous dispersions of the present invention aregenerally prepared by preparing a homogenous blend of the activeingredient and the viscous oil together with the water insolublesolvents if present. Usually heating these components to approximately80°-90° C. facilitates the preparation of the blend. The surfactants,water soluble solvents and modifiers are dissolved in water by heating,preferably to 70°-90° C. to provide an aqueous phase. The aqueous phaseis then added to under high shear conditions to the oil phase, or vicevera.

The invention will be further described by reference examples ofpreferred embodiments in which the compositions are expressed as part byweight.

BRIEF DESCRIPTION Of THE DRAWING

The accompanying drawings are graphs illustrating the results ofexperiments described in the following examples, which illte theinvention.

FIG. 1 relates to Example 1,

FIGS. 2a and 2b relate to Example 2,

FIGS. 3a and 3b relate to Example 3,

FIGS. 4a and 4b relate to Example 4,

FIGS. 5a and 5b relate to Example 7,

FIG. 6 relates to Example 8,

FIG. 7 relates to Example 9,

FIGS. 8a and 8b relate to Example 10,

FIGS. 9a and 9b relate to Example II,

FIG. 10 relates to Example 13,

FIG. II relates to Example 14,

FIGS. 12a and 12b relate to Example 15.

EXAMPLE 1 FORMULATION A BENEFIT OF FORMULATION: REDUCED PHYTOTOXICITY TOWHEAT

MATERIALS

The viscous oil used as the matrix was bitumen of type C170(free ofpropane-deasphalted tar), This bitumen is defined in the AustralianStandard AS2341, entitled "Properties of Residual Bitumens forPavements".

Trifluralin (technical material) was supplied by Nufarm Pry Ltd, PipeRoad, Laverton, Victoria, Australia.

One of the surfactants used to form and stabilise the bituminousdispersion was calcium dodecyl benzene sulphonate (CaDDBS, 68% inbutanol) as supplied by Nufarm Pty Ltd under the trademark Dobenz CA.This surfactant has a HLB of II±1. The non-ionic surfactant* is a mediumchain length alkyl polyoxypropylene polyoxyethylene surfactant, having aHLB of 16.

METHOD OF FORMULATION OF DISPERSION

    ______________________________________                                        a. Oil Phase   Trifluralin    144                                                            Bitumen C170   264                                                            Xylene          72                                                            Dobenz CA       16                                                            Non-ionic surfactant*                                                                         16                                             b. Aqueous Phase                                                                             Water          1,120                                           ______________________________________                                    

The oil phase components were heated together in a 1 liter containerwith mixing and the temperature was allowed to rise to 100° C. Thecontainer was periodically weighed and xylene lost by evaporation wasreplaced. When the oil phase was homogenous, it was poured into thewater phase (water temperature 85° C.), which was contained in a 2 litercontainer. Throughout the addition of oil phase to water phase, thesystem was agitated using a Silverson L4R high shear mixer, with anemulsor screen attached. After 5 minutes the emulsion was cooled to 40°C. using an ice bath.

BIOASSAY PROTOCOL (PHYTOTOXICITY)

The bioassay protocol for the determination of phytotoxicity of theformulation was as follows.

Punnets (140×85×50 mm³) were filled with 500 g of soil, previouslyprepared to a standard moisture content depending on the soil type. Thismoisture was 11% for an acidic sandy loam, as typical of Wonwondah,Victoria, Australia. The soil moisture was 19% for a medium grey clay astypical of Dooen, Victoria, Australia, and was 11% for an alkaline sandyloam, as typical of the Mallee, Victoria, Australia. The punnets weresprayed with trifluralin formulations at a range of rates spanning0-1,500 g trifluralin/ha through a laboratory boom sprayer. The boompasses over the punnets at 6 km/hr and delivers the water plusherbicidal formulation at 64 liters/ha through spraying systems (R)nozzles 11001 at 200 kPa.

Immediately after spraying, the soil in each punnet was mixed thoroughlyin individual plastic bags and then returned to the punnets, and sown towheat. The punnets were then transferred to a glasshouse where they weremaintained at 16° C. and 24° C. for 8 and 16 hours respectively, for 10days, being watered daily to avoid moisture stress.

The effect of the herbicide was assessed 10 days after spraying bydetermining the percentage of wheat seedlings which had emerged from thetreated soil. A dose versus response curve was obtained for eachformulation by fitting a line through the means of each of the sixreplicates. Formulations were deemed to have improved crop safety ifsubstantially more wheat seedlings had emerged at any given applicationrate than from the standard emulsifiable concentrate formulation oftrifluralin (40% active by weight).

RESULTS OF EXAMPLE 1

The results are tabulated in Table 2 and graphed in FIG. 1.

It is apparent from FIG. 1 that in the Mallee soil type used, the use ofFormulation A led to substantially higher emergence of wheat seedlingscompared to the EC (emulsifiable concentrate, 40% actives) which is thestandard formulation supplied by Nufarm Australia). This resultdemonstrates that Formulation A has significantly lower phytotoxicity towheat.

                  TABLE 2                                                         ______________________________________                                        PHYTOTOXICITY: EMERGENCE OF WHEAT                                             VERSUS RATE (MALLEE SOIL) -                                                   EC VERSUS FORMULATION A                                                                         % Emergence                                                 Rate (l/ha)                                                                             Log (rate +)  EC     Formulation A                                  ______________________________________                                        0         0             86     86                                             1.0       0.3           53     75                                             2.0        0.48         10     28                                             3.0       0.6            5     10                                             ______________________________________                                    

EXAMPLE 2 TRIFLURALIN CONTROLLED RELEASE FORMULATION B BENEFIT OFFORMULATION: REDUCED PHYTOXICITY TO WHEAT

MATERIALS AND METHOD OF FORMULATION OF DISPERSION

The oil phase of the formulation consisted of:

    ______________________________________                                        Trifluralin        144                                                        Bitumen C170       68                                                         Xylene             72                                                         Di-isodecyl phthalate                                                                            96                                                         Nonionic surfactant*                                                                             24                                                         Dobenz CA          16                                                         ______________________________________                                    

The water phase consisted of water 1120 parts by weight.

The method of preparing the dispersion was the same as for Example 1.

*see Example 1

BIOASSAY PROTOCOL (PHYTOTOXICITY): As for Example 1.

RESULTS OF EXAMPLE 2

The results are tabulated in Tables 3a and 3b and graphed in FIGS. 2aand 2b.

It is apparent from FIGS. 2a and 2b that on both soil types studied theuse of formulation B led to a substantially higher emergence of wheatseedlings compared to the EC at most application rates. This resultdemonstrates that Formulation B is significantly less phytotoxic towheat.

                  TABLE 3a                                                        ______________________________________                                        PHYTOTOXICITY: EMERGENCE OF WHEAT                                             VERSUS RATE (DOOEN SOIL) -                                                    EC VERSUS FORMULATION B                                                                         % Emergence                                                 Rate (l/ha)                                                                             Log (rate + 1)                                                                              EC     Formulation B                                  ______________________________________                                        0         0             97     97                                             1.0       0.3           33     44                                             2.0        0.48          8     12                                             3.0       0.6            5     11                                             ______________________________________                                    

                  TABLE 3b                                                        ______________________________________                                        PHYTOTOXICITY: EMERGENCE OF WHEAT                                             VERSUS RATE (MALLEE SOIL) -                                                   EC VERSUS FORMULATION B                                                                         % Emergence                                                 Rate (l/ha)                                                                             Log (rate + 1)                                                                              EC     Formulation B                                  ______________________________________                                        0         0             86     86                                             1.0       0.3           35     62                                             2.0        0.48          3     33                                             3.0       0.6            3      9                                             ______________________________________                                    

EXAMPLE 3 TRIFLURALIN CONTROLLED RELEASE FORMULATION

BENEFIT OF FORMULATION: Reduced loss of trifluralin vapour to theatmosphere.

This example uses the same formulation as Example 2. but shows adifferent benefit of the formulation.

BIOASSAY PROTOCOL (VOLATILE LOSS OF ACTIVE)

The bioassay protocol for the determination of efficacy of thetrifluralin formulations was as follows:

Soil was air dried and brought to a given level of water by weight (seebioassay protocol: phytotoxicity). The soil was placed into containersof dimension 85 mm×140 mm×50 mm (depth) and the containers of soil weresprayed at rates of formulation in the range 0-1.5 liters/hectare oftrifluralin emulsifiable concentrate. The standard emulsifiableconcentrate formulation contained 40% trifluralin active. A spray volumeof 60 liters/hectare of water was used, and the dilute formulation weresprayed through Spraying System nozzles of type 11003 using 200kilopascals of air pressure. Ambient temperature was 30°±3° C.

The sprayed containers were treated in two ways:

a. Soil was immediately mixed thoroughly after spraying to effectinstant and complete incorporation of active, and returned to thecontainer.

b. Sprayed soil was left for 48 hours, then mixed as above.

The treated soil portions were bioassayed for trifluralin according tothe following protocol.

Soil portions were sown at 24 hours after spraying with 20 seeds ofannual ryegrass (lollium rigidum) to a depth of 1 cm. The samples werekept at 18°-22° C. in a glasshouse for 10 days, and were watered twicedaily. The results were obtained by calculating the percentage emergencefrom each container of soil.

The results are tabulated and are graphed using points which representthe mean value of six duplicates. The graphs are presented as %emergence vs log₁₀ (dose+1). The numerical value for the dose is inunits of liters per hectare equivalent of trifluralin emulsifiableconcentrate.

In general, efficacy results for controlled release formulations arecompared with efficacy results for the emulsifiable concentrate standardformulation sprayed at the same time.

The difference between the dose response curves corresponding totreatment (a) (immediate incorporation), and (b) (incorporation at t=48hours) was taken to be related to the extent of volatile loss of active.A decrease in this difference would indicate reduced volatile loss.

RESULTS OF EXAMPLE 3

The results are tabulated in Tables 4a and 4b, and graphed in FIGS. 3aand 3b.

FIG. 3a shows the results for EC, which should be compared with FIG. 3bwhich gives the results for Formulation B. In all these experiments, thesoil used was medium grey clay (Dooen).

It was concluded that the loss of efficacy caused by the delay inincorporation was significantly less when Formulation B was used.

                  TABLE 4a                                                        ______________________________________                                        VOLATILISATION EXPERIMENT: EMERGENCE                                          OF WEEDS VERSUS RATE DOOEN SOIL:                                              IMMEDIATE AND DELAYED                                                         INCORPORATION - TRIFLURALIN EC                                                                   % Emergence                                                Rate (l/ha)                                                                             Log (rate + 1) Imm. Inc Del. Inc                                    ______________________________________                                        0         0              86       90                                          1.0       0.08           60       80                                          2.0       0.15           11       42                                          3.0       0.20           15       41                                          1.0       0.30            1       16                                          1.5       0.40            0        2                                          ______________________________________                                    

                  TABLE 4b                                                        ______________________________________                                        VOLATILISATION EXPERIMENT: EMERGENCE                                          OF WEEDS VERSUS RATE DOOEN SOIL:                                              IMMEDIATE AND DELAYED                                                         INCORPORATION - FORMULATION B                                                               % Emergence                                                     Rate (l/ha)                                                                           Log (Rate - 1)                                                                            Immediate Inc.                                                                             Delayed Inc.                                 ______________________________________                                        0       0           88           90                                           0.2     0.08        55           90                                           0.4     0.15         5           20                                           0.6     0.20         1           14                                           1.0     0.30         0            5                                           1.5     0.40         0            1                                           ______________________________________                                    

EXAMPLE 4 TRIFLURALIN CONTROLLED RELEASE FORMULATION C BENEFIT OFFORMULATION: REDUCED PHYTOTOXICITY TO WHEAT MATERIALS (SEE EXAMPLE 1)

METHOD OF FORMULATION OF DISPERSION C

The dispersion consisted of:

    ______________________________________                                        Component             Parts w/w %                                             ______________________________________                                        Oil Phase                                                                     Trifluralin (technical grade)                                                                       20.26                                                   Bitumen C170 PD Tar free                                                                            35.80                                                   Xylene                11.48                                                   Aqueous Phase                                                                 Water                 24.65                                                   Dobenz CA              2.09                                                   nonionic surfactant* (see Example I)                                                                 1.39                                                   Glycerol               4.33                                                   ______________________________________                                    

The oil phase was prepared by blending the melted bitumen andtrifluralin and xylene until homogenous at 90° C.

The aqueous phase was prepared by dissolving the components in the waterat 80° C.

The oil phase was heated to 100° C. prior to emulsification. The aqueousphase (80° C.) was added to the oil phase and emulsified using aSilverson homogenizer with a 16 mm disintegrating head at 2/3 maximumspeed for 2 minutes.

The resulting emulsion had a viscosity of 1500 cp. The droplet size ofthe emulsion was typically less than 2 um. After two months torage atambient temperature there was no sign of trifluralin crystallization,droplet coalescence or emulsion deterioration as determined bytechniques well known in the art.

Formulation C was the same as Formulation A in terms of matrixcomposition but the oil phase ratio percentage much higher.

BIOASSAY PROTOCOL (PHYTOTOXICITY): See Example 1

RESULTS OF EXAMPLE 4

The results are tabulated in Tables 5a and 5b and are graphed in FIGS.4a and 4b.

It is apparent from FIGS. 4a and 4b that on both soil types studied atDooen and Mallee respectively, the use of Formulation C led to a higheremergence of wheat seedlings compared to the EC at most applicationrates. This demonstrates that Formulation C was significantly lessphytotoxic to wheat.

                  TABLE 5a                                                        ______________________________________                                        PHYTOTOXICITY: EMERGENCE OF WHEAT VERSUS                                      RATE DOOEN SOIL: EC VERSUS - FORMULATION C                                                      % Emergence                                                 Rate (l/ha)                                                                             Log (rate + 1)                                                                              EC     Formulation C                                  ______________________________________                                        0         0             90     90                                             1.0       0.30          43     60                                             2.0       0.48           2     20                                             3.0       0.06           3     12                                             ______________________________________                                    

                  TABLE 5b                                                        ______________________________________                                        PHYTOTOXICITY: EMERGENCE OF WHEAT VERSUS                                      RATE MALLEE SOIL: EC VERSUS - FORMULATION C                                                     % Emergence                                                 Rate (l/ha)                                                                             Log (rate + 1)                                                                              EC     Formulation C                                  ______________________________________                                        0         0             88     88                                             1.0       0.30          29     73                                             2.0       0.48           5     39                                             3.0       0.06           2     10                                             ______________________________________                                    

EXAMPLE 5

An emulsion of the type suitable for use as a pre-emergent herbicide wasprepared using the following components according to the procedurebelow.

    ______________________________________                                        Component          Part w/w %                                                 ______________________________________                                        Oil Phase                                                                     Trifluralin technical grade                                                                      20.26                                                      Bitumen PD tar free                                                                              29.29                                                      Xylene             11.48                                                      Di-isodecyl phthalate                                                                             6.51                                                      Aqueous Phase                                                                 Water              28.96                                                      Calcium dodecyl benzene                                                                           2.10                                                      sulphonate (68% active)                                                       Non-ionic surfactant**                                                                            1.40                                                      ______________________________________                                         The nonionic surfactant** is an alkyl polyoxypropylene polyoxyethylene        condensate where alkyl is C.sub.3 -C.sub.8 the polyoxypropylene is 67-77      moles; and the polyoxyethylene is 70-80 moles.                           

The oil phase was prepared by blending the components at 90° C. untilfluid and homogeneous and heating to 100° C. prior to emulsification.

The emulsifier was dissolved in the aqueous phase at 800° C.

The aqueous phase was added to the oil phase and emulsified using aSilverson homogenizer with a 16 mm disintegrating head at 2/3 maximumspeed for 2 minutes.

The resulting emulsion had a viscosity of 1800 cp. The droplet size wastypically less than 2 um. After one month storage at ambient temperaturethe emulsion showed no signs of trifluralin crystallization, dropletcoalescence or deterioration as determined by techniques commonlyemployed in the art.

EXAMPLE 6

An emulsion suitable for use as a pre-emergent herbicide was preparedusing the following components according to the procedure below.

    ______________________________________                                                 Component       Part w/w %                                           ______________________________________                                        Oil Phase  Trifluralin technical grade                                                                     20.26                                                       Bitumen C170 PD Tar free                                                                        35.80                                                       Xylene            11.48                                            Aqueous Phase                                                                            Water             24.62                                                       Calcium dodecyl benzene                                                                         1.755                                                       Sulphonate (68% active)                                                       Nonionic surfactant*                                                          (see Example 1)   1.755                                                       Glycerol          4.34                                             ______________________________________                                    

The oil phase was heated to 100° C. prior to emulsification. The aqueousphase (at 80° C.) was added to the oil phase and emulsified using aSilverson homogenizer with a 16 mm disintegrating head for 2 minutes.

EXAMPLE 7 TRIFLURALIN, CONTROLLED RELEASE FORMULATION D.BENEFIT OFFORMULATION: INCREASED POTENCY OF TRIFLURALIN

MATERIALS

The oil phase of the formulation consisted of

    ______________________________________                                        Trifluralin             96                                                    Chinese Rosin           72                                                    (natural product substantially abietic                                        acid ex China)                                                                Solvesso 150            72                                                    Nonionic surfactant* (see Example 1)                                                                  14                                                    Dobenz CA                6                                                    ______________________________________                                    

The water phase consisted of 560 parts.

METHOD OF FORMULATION Of DISPERSION D

Trifluralin and Chinese rosin were heated together until homogeneous at100° C. and then solvesso 150 and Dobenz CA were added and stirred. Thisoil phase (90° C.) was added to water (90° C.) in the presence of highshear agitation provided by a Silverson L4R high shear mixer. Particlesize was 1-3 microns.

BIOASSAY PROTOCOL: (As for volatile loss of active--see Example 3)

RESULTS OF EXAMPLE 7

The results are tabulated in Tables 6(a), 6(b) and graphed in FIGS. 5(a)and 5(b). FIG. 5(a) shows the results for EC, which should be comparedwith FIG. 5(b) which gives the results for Formulation D. For all theseexperiments the soil used was an alkaline sandy loan as typical of theMallee, Victoria, Australia.

It was concluded that Formulation D was significantly more potent thanwas the EC both under conditions of immediate and delayed incorporation.

                  TABLE 6 (a)                                                     ______________________________________                                        TRIFLURALIN EC                                                                POTENCY EXPERIMENT - EMERGENCE                                                OF WEEDS ON RATE.                                                             MALLEE SOIL. IMMEDIATE AND DELAYED                                            INCORPORATION.                                                                                  % Emergence                                                 Rate (1/ha)                                                                           Log.sub.10 (rate + 1)                                                                         Imm. Inc. Del. Inc.                                   ______________________________________                                        0       0               90        95                                          0.1     0.05            90        90                                          0.2     0.09            94        90                                          0.3     0.12            72        82                                          0.4     0.15            41        70                                          0.6     0.2             19        73                                          0.8     0.26            10        64                                          1       0.3              1        35                                          1.5     0.4              3        22                                          ______________________________________                                    

                  TABLE 6 (b)                                                     ______________________________________                                        TRIFLURALIN FORMULATION D.                                                    POTENCY EXPERIMENT - EMERGENCE OF WEEDS                                       ON RATE. MALLEE SOIL.                                                         IMMEDIATE AND DELAYED INCORPORATION.                                          Rate (1/ha)             % Emergence                                           EC Equivalent                                                                            Log.sub.10 (rate + 1)                                                                      Imm. Inc.  Del. Inc.                                  ______________________________________                                        0          0            90         95                                         0.1        0.05         89         92                                         0.2        0.09         92         90                                         0.3        0.12         47         78                                         0.4        0.15         28         84                                         0.6        0.2           8         48                                         0.8        0.26          8         33                                         1          0.3           3         10                                         1.5        0.4           1          3                                         ______________________________________                                    

EXAMPLE 8 TRIFLURALIN CONTROLLED RELEASE FORMULATION E BENEFIT OFFORMULATION: REDUCED PHYTOTOXCITY TO WHEAT

MATERIALS AND METHOD OF FORMULATION OF DISPERSION E

The oil phase of the formulation consisted of

    ______________________________________                                        Trifluralin       96                                                          Chinese rosin     48                                                          Solvesso 150      96                                                          Nonionic surfactant*                                                                            14                                                          Dobenz CA          6                                                          ______________________________________                                    

The water phase consisted of 560 pans. The method used was as forExample 7.

*see Example 1

BIOASSAY PROTOCAL (PHYTOTOXITY) As for Example 1

RESULTS OF EXAMPLE 8

The results are tabulated in Table 7, which includes control datarelating to EC, and are graphed in FIG. 6.

                  TABLE 7                                                         ______________________________________                                        PHYTOTOXCITY: EMERGENCE OF WHEAT                                              VESUS RATE                                                                    MALLEE SOIL - EC & TRIFLURALIN FORMULATION E                                                          % Emergence                                           Rate (1/ha)                                                                             Log.sub.10 (rate + 1)                                                                       EC      Formulation E                                 ______________________________________                                        0         --            98      98                                            0.6       --            65      69                                            0.8       --            52      66                                            1         --            47      55                                            1.5       --            40      51                                            2         --            12      12                                            2.5       --             6       9                                            ______________________________________                                    

It is apparent from FIG. 6 that the use of Formulation E on Mallee soilled to a substantially higher emergence of wheat seedlings compared toEC at most application rates. This result demonstrates that FormulationE is less phytotoxic to wheat.

EXAMPLE 9

    ______________________________________                                        TRIFLURALIN CONTROLLED RELEASE                                                FORMULATION F                                                                 BENEFIT OF FORMULATION: REDUCED                                               PHYTOTOXICITY TO WHEAT                                                        MATERIALS AND METHOD OF FORMULATION OF                                        DISPERSION F                                                                  ______________________________________                                        The oil phase of the formulation consisted of                                 Trifluralin              168                                                  Chinese Rosin            144                                                  Estergum SA               48                                                  (glycerol ester of abietic acid, manufactured                                 by Frankston Manufacturing Co., Victoria)                                     Solvesso 150             120                                                  Nonionic surfactant* (see Example 1)                                                                    28                                                  Dobenz CA                 12                                                  ______________________________________                                    

The water phase consisted of 1,120 parts. The method used was as forexample 7.

BIOASSAY PROTOCOL (PHYTOTOXICITY) As for Example 1.

RESULTS OF EXAMPLE 9

The results are tabulated in Table 8 which includes control datarelating to EC, and are graphed in FIG. 7.

                  TABLE 8                                                         ______________________________________                                        PHYTOTOXCITY: EMERGENCE OF WHEAT                                              VESUS RATE                                                                    MALLEE SOIL - EC & TRIFLURALIN FORMULATION F                                                          % Emergence                                           Rate (1/ha)                                                                             Log.sub.10 (rate + 1)                                                                       EC      Formulation F                                 ______________________________________                                        0         --            98      98                                            0.6       --            62      84                                            0.8       --            42      72                                            1         --            39      46                                            1.5       --            18      21                                            2         --             3      16                                            2.5       --             2       8                                            ______________________________________                                    

It is apparent from FIG. 7 that the use of Formulation F on Mallee soilled to a higher emergence of wheat seedlings compared to EC at mostapplication rates. This result demonstrates that Formulation F is lessphytotoxic to wheat.

EXAMPLE 10 TRIFLURALIN CONTROLLED RELEASE FORMULATION G BENEFIT OFFORMULATION; INCREASED POTENCY OF TRIFLURALIN

    ______________________________________                                        Materials                                                                     ______________________________________                                        Trifluralin       120                                                         Chinese rosin     72                                                          Solvess 150       48                                                          Nonionic surfactant*                                                                            14                                                          Dobenz CA          6                                                          ______________________________________                                    

The water phase consisted of 560 parts. The method was as for Example 7.

* see Example 1

BIOASSAY PROTOCOL (AS FOR VOLATILE LOSS OF ACTIVE--SEE EXAMPLE 3)

RESULTS OF EXAMPLE 10

The results are tabulated in Tables 9(a), 9(b) and graphed in FIGS. 8(a)and 8(b). FIG. 8(a) shows the results for EC which should be comparedwith FIG. 8(b) which gives the results for Formulation G. Mallee soilwas used in all experiments. It was concluded that Formulation G wassignificantly more potent than was the EC both under conditions ofimmediate and delayed incorporation.

                  TABLE 9 (a)                                                     ______________________________________                                        TRIFLURALIN EC (40% ACTIVE)                                                   POTENCY EXPERIMENT - EMERGENCE OF                                             WEEDS VS RATE                                                                 MALLEE SOIL. IMMEDIATE AND                                                    DELAYED IN CORPORATION                                                                          % Emergence                                                 Rate 1/ha                                                                             Log.sub.10 (rate + 1)                                                                         Imm. Inc. Del. Inc.                                   ______________________________________                                        0       0               90        95                                          0.1     0.05            90        90                                          0.2     0.09            92        90                                          0.3     0.12            94        82                                          0.4     0.15            41        70                                          0.6     0.2             19        73                                          0.8     0.26            10        64                                          1       0.3              1        35                                          1.5     0.4              3        22                                          ______________________________________                                    

                  TABLE 9 (b)                                                     ______________________________________                                        TRIFLURALIN FORMULATION G                                                     POTENCY EXPERIMENT - EMERGENCE OF                                             WEEDS VS RATE                                                                 MALLEE SOIL. IMMEDIATE AND                                                    DELAYED INCORPORATION                                                                           % Emergence                                                 Rate 1/ha                                                                             Log.sub.10 (rate + 1)                                                                         Imm. Inc. Del. Inc.                                   ______________________________________                                        0       0               90        95                                          0.1     0.05            91        96                                          0.2     0.09            86        91                                          0.3     0.12            30        93                                          0.4     0.15            19        69                                          0.6     0.2             10        46                                          0.8     0.26             2        15                                          1       0.3              1         7                                          1.5     0.4              0         3                                          ______________________________________                                    

EXAMPLE 11 TRIFLURALIN CONTROLLED RELEASE FORMULATION H BENEFIT OFFORMULATION: INCREASED POTENCY OF TRIFLURALIN

MATERIALS

    ______________________________________                                        Trifluralin       192                                                         Chinese rosin     48                                                          Solvess 150       240                                                         Nonionic surfactant*                                                                            28                                                          Dobenz CA         12                                                          ______________________________________                                    

The water phase consisted of 1,120 parts. The method was as for Example7.

* see Example 1

BIOSSAY PROTOCAL (AS FOR VOLATILE LOSS OF ACTIVE--SEE EXAMPLE 3)

RESULTS OF EXAMPLE 11

The results are tabulated in Tables 10(a), 10(b) and graphed in FIGS.9(a) and 9(b). FIG. 11(a) shows the results for EC which should becompared with FIG. 9(b) which gives the results for Formulation H. Itwas concluded that formulation H was significantly more potent than wasthe EC.

                  TABLE 10 (a)                                                    ______________________________________                                        TRIFLURALIN EC (40% ACTIVE)                                                   POTENCY EXPERIMENT: EMERGENCE                                                 OF WEEDS VS RATE MALLEE SOIL -                                                IMMEDIATE AND DELAYED INCORPORATION                                                                           % Emergence                                   Rate 1/ha                                                                             Log.sub.10 (rate + 1)                                                                       Imm. Inc. Del. Inc.                                     ______________________________________                                        0       0             95        85                                            0.1     0.05          97        87                                            0.2     0.09          73        77                                            0.3     0.12          34        89                                            0.4     0.15          20        84                                            0.6     0.2            5        60                                            0.8     0.26           2        32                                            1       0.3            1        18                                            1.5     0.4            0         3                                            ______________________________________                                    

                  TABLE 10 (b)                                                    ______________________________________                                        TRIFLURALIN FORMULATION H                                                     POTENCY EXPERIMENT: EMERGENCE                                                 OF WEEDS VS RATE MALLEE SOIL -                                                IMMEDIATE AND DELAYED INCORPORATION                                                                           % Emergence                                   Rate 1/ha                                                                             Log.sub.10 (rate + 1)                                                                       Imm. Inc. Del. Inc.                                     ______________________________________                                        0       0             95        80                                            0.1     0.05          85        85                                            0.2     0.09          55        92                                            0.3     0.12          10        86                                            0.4     0.15           6        81                                            0.6     0.2            2        40                                            0.8     0.26           1        10                                            1       0.3            0         2                                            1.5     0.4            0         3                                            ______________________________________                                    

EXAMPLE 12

An emulsion suitable for use as a pre-emergent herbicide was preparedusing the following components according to the procedure below.

    ______________________________________                                        Component            Part                                                     ______________________________________                                        Oil Phase                                                                     Trifluralin          26                                                       Chinese rosin        19.5                                                     Solvesso 150         19.5                                                     Dobenz CA            0.5                                                      Water phase                                                                   Water                28.5                                                     Polyetheylenglycol (MW300)                                                                         4                                                        Nonionic surfactant* 2                                                        ______________________________________                                         *see Example I                                                           

METHOD

In a 1 liter container were added 240 g of trifluralin and 180 g ofChinese rosin, and heated to 105° C. with stirring until homogeneous.Weight loss was 1.5 g (0.36%). 180 g of Solvesso 150 was added and themixture was stirred, the temperature thereby dropping to 75° C. Themixture was further stirred until the temperature reached 58° C. Weightloss was 0.5 g which was replenished by Solvesso 150. The mixture wasdecanted into jars which were tightly sealed. The mixture remainedliquid at -5° C.

In a 100 ml beaker was added 0.4 g of Dobenz CA and 52 g of theabove-mentioned mixture (oil phase), and heated with stirring to 95° C.

The water phase was prepared by adding 1.6 g nonionic surfactant* 3.2 gof PEG 300 and 22.8 g of boiling water to a 100 ml beaker.

The beaker containing the water phase was agitated using the 16 mmdisintegrating head on a Silverson homogenizer. The oil phase wasgradually added, and care was taken to ensure that the surface of theliquid in the beaker was continuously homogenised by adjusting theheight of the disintegrating head. When addition of the oil phase wascomplete, the emulsion was further homogenised for 30 minutes.

* see Example 1

EXAMPLE 13 METOLACHLOR FORMULATION 1

The emulsion in this example contained the herbicide metolachlor whichis of the chloro acetanilide class.

    ______________________________________                                        MATERIALS                                                                     ______________________________________                                        Metolachlor         36                                                        Bitumen C170, PD tar free                                                                         42                                                        Di-isodecyl phthalate                                                                             24                                                        Xylene              18                                                        Nonionic surfactant*                                                                               6                                                        Dobenz CA            4                                                        ______________________________________                                    

The water phase consisted of 280 parts.

* see Example 1

METHOD

Metolachlor, bitumen, di-isodecyl phthalate and nonionic surfactant weremixed at 110° C. until homogeneous. Xylene and Dobenz CA were added andthe weight loss replenished using xylene. The above oil phase was slowlyadded to water which was agitated using a Silverson homogenizer.

BIOASSAY PROTOCOL

This protocol was as for the volatile loss of active in Example 3 withthe following modifications:

(i) The metolachlor was sprayed through a laboratory sprayer capable ofsimulating field conditions. Applications were at a pressure of 200 kpa,through nozzles giving a 100 degree flat fan in 64 1/ha water and at 6kilometers per hour.

(ii) Formulations were applied at 0, 18, 36, 72, 144, 216, 288 and 432 gmetolachlor/ha.

(iii) All treatments were incorporated immediately after spraying andpunnets were then each sown to 25 seeds of annual rye grass (holiumrigidum).

(iv) Treatments were assessed for emergence 10 days safter spraying andall seedlings with a height in excess of 20 mm were counted as havingsatisfactorily emerged.

RESULTS OF EXAMPLE 13

The results are tabulated in Table 11 and graphed in FIG. 10. FIG. 10also shows control data for the performance of EC (Dual, 72% activesupplied by Ciba-Geigy Australia) which should be compared withFormulation 1. It was concluded that Formulation 1 was significantlymore potent than EC.

                  TABLE II                                                        ______________________________________                                        METOLACHLOR FORMULATION I                                                     POTENCY EXPERIMENT - EMERGENCE OF                                             WEEDS VS RATE MALLEE SOIL.                                                    IMMEDIATE INCORPORATION EC (72% ACTIVE)                                       AND METOLACHLOR FORMULATION I                                                 Rate (1/h)                      % Emergence                                   EC equivalent                                                                            Log.sub.10 (rate + 1)                                                                      EC      Metol. I                                      ______________________________________                                        0          --           90      90                                            0.03       --           95      85                                            0.06       --           95      93                                            0.11       --           93      84                                            0.2        --           70      41                                            0.3        --           37      14                                            0.4        --           20       4                                            ______________________________________                                    

Example 14 METOLACHLOR FORMULATION J BENEFIT OF FORMULATION: Increasedpotency of metolachlor.

MATERIALS

    ______________________________________                                        Metolachlor         36                                                        Bitumen C170 PD tar free                                                                          66                                                        Xylene              18                                                        Nonionic surfactant*                                                                               6                                                        Dobenz CA            4                                                        ______________________________________                                    

The water phase consisted of 280 parts,

* see Example 1

METHODS

As for Example 13.

BIOASSAY PROTOCOL

As for Example 13.

RESULTS OF EXAMPLE 14

The results are tabulated in Table 12 and graphed in FIG. 11. FIG. 11also shows control data for the performance of EC which should becompared with Formulation J. It was concluded that Formulation J wassignificantly more potent than EC.

                  TABLE 12                                                        ______________________________________                                        METOLACHLOR FORMULATION J                                                     POTENCY EXPERIMENT - EMERGENCE OF                                             WEEDS VS RATE. MALLEE SOIL.                                                   IMMEDIATE INCORPORATION. EC (72% ACTIVE)                                      AND METOLACHLOR FORMULATION J                                                 Rate (1/h)                      % Emergence                                   EC equivalent                                                                            Log.sub.10 (rate + 1)                                                                      EC      Metol. J                                      ______________________________________                                        0          --           90      90                                            0.03       --           95      90                                            0.06       --           95      81                                            0.11       --           93      88                                            0.2        --           70      31                                            0.3        --           37      10                                            0.4        --           20       3                                            ______________________________________                                    

EXAMPLE 15 CHLORPYRIFOS FORMULATION K BENEFIT OF FORMULATION: Reducedvolatile loss of chlorpyrifos.

MATERIALS

    ______________________________________                                        Chlorpyrifos (technical, ex. Nufarm)                                                                 6                                                      Rosin ester            21                                                     Nonionic surfactant*   1.1                                                    Dobenz CA              1.9                                                    ______________________________________                                    

The water phase consisted of 70 parts of water and 0.1 parts keltrol, acellulosic thickener consisting of a high molecular weight xantham gummade by Kelco Division of Merc & Co USA.

* see Example 1

METHOD

Nonionic surfactant, rosin ester and chlorpyrifos were heated at 145° C.and stirred until homogeneous. Subsequently Dobenz CA was added and themixture was again stirred. The emulsion was formed by adding oil phase(115° C.) to boiling water in the presence of high shear agitationsupplied by a Silverson homogenizer. After addition of the oil phase wascomplete, the emulsion was cooled to 40° C. and Keltrol was added withrapid agitation for a further 2-3 minutes.

BIOASSAY PROTOCOL: Reduced volatile loss

(a) GLASS SUBSTRATE

Glass petri dishes were treated with 1 ml of insecticide formulation(log series from 10⁻⁹ to 10⁻⁴ grams active ingredient/ml). Fivereplicates of each dose for each formulation were treated and left todry overnight. On day 2, freshly emerged adult. Apanteles Subandinus (10individuals) were added to each replicate plus 5 untreated controls.Mortality was assessed after 24 hours (day 3).

(b) LEAF BIOASSAY, GLASS-HOUSE

Potato plants (S. Tuberosum) were grown in pots in a glass-house(temperatures up to 35° C.) and each plant was sprayed by hand untilrunoff with formulations of chlorpyrifos (10⁻⁷ grams active ingredientper ml). Leaves were picked on several days after spraying andbioassayed at 23° C. with Apanteles Subandinus. Disks (2 cm diameter)were cut from the leaves and placed in a glass petri dish (10discs/petri dish) with A. Subandinus (10/ dish). 5 petri dishes wereused for each formulation and the control. The mortality of A.Subandinus was assessed as for the above bioassay.

RESULTS OF EXAMPLE 15

The results are tabulated in Tables 13(a) and 13(b) for the glasssubstrate and leaf bioassay respectively, and control data is also shownfor the performance of the EC (Lorsban, by Dow Elanco). The results arealso graphed in FIGS. 12(a) and 12(b). On the glass substrate test (FIG.12(a)) chlorpyrifos formulation K killed A. Subandinus at much lowerdose than Lorsban. The estimated LD50 for Formulation K was two ordersof magnitude lower than for Lorsban.

On the leaf substrate (glass-house) test (FIG. 12(b)), Lorsban killedhigh numbers of A. Subandinus for only one day while chlorpyrifosformulation K killed high numbers for over 7 days.

                  TABLE 13(a)                                                     ______________________________________                                        CHLORPYRIFOS FORMULATION K                                                    VOLATILE LOSS EXPERIMENT:                                                     Glass Substrate EC (Lorsban 50) and Formulation K                             Dosage              Percent Mortality                                         (Micrograms chlorpyrifos per dish)                                                                EC      Formulation K                                     ______________________________________                                        1,000               100     100                                               20                  100     100                                               2                    26     100                                               0.2                  8       90                                               0.02                 5       8                                                ______________________________________                                    

                  TABLE 13(b)                                                     ______________________________________                                        CHLORPYRIFOS FORMULATION K                                                    VOLATILE LOSS EXPERIMENT:                                                     Leaf Bioassay EC (Lorsban 50) and Formulation K                                               Percent Mortality                                             Days After Application                                                                          EC     Formulation K                                        ______________________________________                                        1                 100    100                                                  3                 25     100                                                  9                 22      75                                                  22                 0      0                                                   ______________________________________                                    

EXAMPLE 16 CHLORPYRIFOS FORMULATION L BENEFIT OF FORMULATION: Reducedvolatile loss of chlorpyrifos

MATERIALS

    ______________________________________                                        Chlorpyrifos      48                                                          Rosin ester       60                                                          Nonionic surfactant*                                                                            6                                                           Dobenz CA         6                                                           Water             280                                                         Keltrol           0.6                                                         ______________________________________                                    

The method was as for Example 15.

* see Example 1

BIOASSAY PROTOCOL: Reduced volatile loss, glass substrate (as for E15)

RESULTS

The results were that the estimated LD 50 for Formulation L was 2 ordersof magnitude lower than for Lorsban and data are shown in Table 14.

                  TABLE 14                                                        ______________________________________                                        CHLORPYRIFOS FORMULATION L                                                    VOLATILE LOSS EXPERIMENT - GLASS SUBSTRATE                                    Dosage              Percent Mortality                                         (micrograms chlorpyrifos per disk)                                                                EC      Formulation L                                     ______________________________________                                        1,000               100     100                                               20                  100     100                                               2                    22     100                                               0.2                  10      66                                               ______________________________________                                    

Since modifications within the spirit and scope of the invention may bereadily effected by persons skilled in the art, it is to be understoodthat the invention is not limited to the particular embodimentsdescribed, by way of example, hereinabove.

We claim:
 1. A controlled release composition comprising an aqueousdispersion of a water insoluble matrix as a disperse phase wherein saidmatrix contains at least one active ingredient having a melting point ofless than about 140° C. selected from the group consisting ofherbicides, insecticides, fungicides and nematicides, and wherein saidmatrix comprises a viscous oil selected from the group consisting ofbitumen, abietic acid, ester derivatives of abietic acid, carboxylicacid containing materials, and carboxylic acid ester containingmaterials; characterized in that said active ingredient is soluble insaid matrix.
 2. A composition according to claim 1 wherein said activeingredient has a melting point less than 120° C.
 3. A compositionaccording to claim 1 wherein said active ingredient has a melting pointless than 80° C.
 4. A composition according to claim 1 wherein theactive material is either a chloroacetanilide or dinitroanilineherbicide or an organophosphate insecticide.
 5. A Composition accordingto claim 1, further comprising at least one surfactant selected from thegroup consisting of non-ionic surfactants, and anionic surfactants.
 6. Acomposition according to claim 5, wherein a said anionic surfactant is acalcium salt of an alkyl benzene sulphonic acid, and a said non-ionicsurfactant comprises a polyethylene oxide and polypropylene oxidecopolymer or adduct thereof.
 7. A composition according to claim 1wherein the composition further comprises a non-volatile diluent havingester functionality.
 8. A composition according to claim 1 or 7, whereinsaid composition further comprises a volatile solvent at a ratio ofsolid volatile solvent to active ingredient of about 0.5 to 1.5.
 9. Acomposition according to claim 1, 7 or 8 wherein the active ingredientcomprises at least 15% by weight of the composition and the dispersephase comprises at least 50% by weight of the composition.
 10. Acomposition according to any one of claim 1 wherein the activeingredient is selected from the group consisting of trifluralin,chlorpyrifos and metolachlor.
 11. A method of treating soil to retardthe growth of vegetation thereon, comprising applying to the soil acontrolled release composition according to any claim 9, wherein theactive ingredient is a herbicide.
 12. A method of rendering insectsineffective by using a controlled release composition according to claim1, wherein the active ingredient is an insecticide.
 13. A compositionaccording to claim 1, wherein when said viscous oil is bitumen, saidcomposition further comprises an anionic surfactant that is a calciumsalt of an alkyl benzene sulphonic acid and a non-ionic surfactant thatis a polyethylene oxide and polypropylene oxide copolymer or adductthereof.
 14. A composition according to claim 10 wherein when saidactive ingredient is trifluralin, said viscous oil is selected from thegroup consisting of rosin, Chinese rosin, and rosin ester.